172 EXTINCT AND VANISHING MAMMALS 



came, and that they are frequently hunted by the natives." (Cool- 

 idge, 1936, pp. 493, 499.) 



According to all accounts, Gorillas still occur in fair numbers in 

 the Sanga River region, though not so commonly as 25 years ago.~A 

 local French doctor, in the course of two years, had treated nine 

 natives for Gorilla attack, one of the cases being fatal. (J. A. G. 

 Rehn, oral communication, March 22, 1939.) 



Belgian Congo. Schouteden (19306, pp. 298-299) presents evi- 

 dence of the rare occurrence of Gorillas in the Mayumbe forest, 

 north of the lower reaches of the Congo River. Later (19366, 

 pp. 15-16) he records a skull from the Haut Mayumbe. Here the 

 animal had seemed to have disappeared, or to occur only occasion- 

 ally, coming perhaps from Gabun. But it appears to occur still in 

 certain parts of Mayumbe, thanks, perhaps, to the protection it has 

 enjoyed for some years. 



Use in research. Yerkes and Yerkes point out (1929, p. 590) 

 that the Gorilla and other anthropoid apes "must inevitably become 

 the preferred substitutes for human subjects in investigations which 

 may not be carried on with the latter and which have as objectives 

 the extension of knowledge and control of human life." They also 

 stress (p. 589) the greater availability and controllability of these 

 animals for use in the investigation of various problems in genetics, 

 physiology, neuro- and psychopathology, psychology, sociology, 

 pedagogy, and experimental education. 



Survival Yerkes and Yerkes (1929, p. 396) quote Keith (1896) 

 as follows: "From accounts furnished by travellers and hunters, one 

 infers that the total population [of the species as a whole] males, 

 females, and young is well under 10,000." Eventually (1914) 

 Keith raised this estimate to 20,000 to 30,000 individuals, but 

 Yerkes and Yerkes remark (p. 397) that it is difficult to decide how 

 seriously this estimate should be taken. They also say (p. 397) : 



"Concerning abundance or frequency little is known. Both early 

 and late in the last century the relative rarity of the gorilla sug- 

 gested to investigators its disappearance and probable extinction. 

 From limited distribution, difficulty of negro hunters in procuring 

 skins of adults, and the small number of captive specimens sent to 

 Europe, Deniker (1891, pp. 369-370) infers that the process of 

 extinction is under way. . . . 



"For nearly a century it has been known that the gorilla is the 

 rarest of the manlike apes." 



H. C. Raven (oral communication, March 17, 1937) estimates 

 the total number of all Gorillas now living at more than 1,000 and 

 at less than 10,000. 



